AMD has confirmed that its upcoming Ryzen 7 5800X3D processor with a 96MB L3 cache aimed at gamers will not support overclocking. The official reason is that AMD's 3D V-Cache cannot really work at high voltages. That said, it remains to be seen for how long the CPU will work at its boost clocks.
"As people know, this is our first CPU with 3D V-Cache technology [...] and that packaging technology in our space has different voltage and frequency scaling than people may be accustomed with," said Robert Hallock, director of technical marketing at AMD, during a HotHardware broadcast (45:44). "On the desktop parts you've seen us ship parts that range up to 1.45V or even 1.5V in boost and that is not the limit for 3D V-Cache. The voltage limit on that is more like 1.3V to 1.35V."
AMD has never listed the overclocking capability of its Ryzen 7 5800X3D processor, so it is not particularly surprising that the part does not support it. Meanwhile, this is the first time when AMD publicly acknowledges this, but 3D V-Cache voltage is a rather surprising reason. Initially, observers thought that because AMD installs its 3D V-Cache on top of Zen 3's 'built-in' L3 cache and then links them using through silicon vias (TSVs). This makes die surface non-uniform and to make it even, the company installs structural silicon spacers on top of Zen 3 general-purpose cores. These spacers trap some heat between the die, structural silicon, and integrated heat spreader.
Perhaps, structural silicon and its effect on heat dissipation adds to AMD's unwillingness to enable overclocking of its Ryzen 7 5800X3D part, but it looks like 3D V-Cache voltage range is the main reason.
| Header Cell - Column 0 | Cores | Threads | L3 Cache | P-Core Base/Boost | TDP / PBP / MTP |
|---|---|---|---|---|
| Ryzen 7 5800X3D | 8P | 16 threads | 96MB | 3.4 / 4.5 GHz | 105W |
| Ryzen 7 5800X | 8P | 16 threads | 32MB | 3.8 / 4.7 GHz | 105W |
| Ryzen 9 5900X | 12P | 24 threads | 32MB | 3.7 / 4.8 GHz | 105W |
In fact, to ensure stable operation of the CPU, AMD had to reduce base frequency of the Ryzen 7 5800X3D by 400MHz and boost clock by 200MHz when compared to the regular Ryzen 7 5800X, so overclocking might really be a bad idea of the processor. Good news is that AMD believes that the extra cache will not only compensate lower clocks, but will allow make the Ryzen 7 5800X3D part a better choice for gaming. Meanwhile, it should be noted that AMD stresses gaming performance, so 3D V-Cache may not be that efficient for other types of applications.
"So, we are not going to allow CPU frequency overclocking or core voltage adjustment because out-of-the-box the design of the chip already uses ranges up to that voltage and frequency limit. On the other hand, fabric overclocking remains enabled, memory overclocking remains enabled, and we know that our parts get the most benefit from that anyway. […] We are working very hard to maximize our out-of-box performance for people and this is a very new thing we are trying."
